An avalanche radiation detector is known for example from Curt Rint: “Handbook for high-frequency and electrical engineers”, 12th edition, Hüthig und Pflaum Verlag Munich/Heidelberg, page 478, incorporated herein by reference. In this case an avalanche region is located on one side of a planar semiconductor substrate and located on the opposite side is a radiation inlet window for the radiation to be detected, which generates free charge carriers in the semiconductor substrate. The free charge carriers generated by the radiation to be detected are accelerated in the avalanche region by the electric field located there and produce new charge carriers in an avalanche fashion which can be detected as a current flow. The electric field strength in the avalanche region is in this case adjusted by a control electrode which is arranged on the side of the avalanche radiation detector opposite to the avalanche region.
A disadvantage with this arrangement of the control electrode is that as the thickness of the avalanche radiation detector increases and the distance between the control electrode and the opposed avalanche region increases accordingly, corresponding high control voltages must be used to adjust the electric field strength in the avalanche region to the desired value.
However, an exact adjustment of the electric field strength in the avalanche region is important since, if the field strength in the avalanche region is too low, the sensitivity suffers, whereas the noise increases with the electric field strength in the avalanche region since stochastically generated charge carriers can also result in avalanche formation.
The maximum thickness of the known avalanche radiation detector is thus limited by the maximum permissible control voltage at the control electrode. However, in order to achieve the highest possible sensitivity, it is desirable that the avalanche radiation detector has the largest possible volume of photosensitive region which, however, is only possible to a limited extent because of the afore-mentioned thickness limitation. On the other hand, it is difficult to expand the photosensitive region in the lateral direction because large-area avalanche regions are difficult to produce from the production technology point of view due to the required structural accuracy of the pn junctions.
It is thus the object of the invention to provide an avalanche radiation detector which makes it possible to achieve enhanced sensitivity.